Trail vs Marathon : pourquoi ton alimentation doit changer quand le te

Trail vs Marathon: why your nutrition needs to change when the terrain changes

INTRODUCTION

It is still early. The air is cool, almost still.

Around you, headlamps form a silent line already winding toward the mountain. You adjust your pack, feel that mix of excitement and uncertainty, and somewhere, a question comes back: "Did I plan the right things to eat?"

Because in trail running, more than in any other endurance discipline, nutrition is not a detail. It is often what makes the difference between a well-controlled race… and a long downward spiral.

Two worlds, two logics

For a long time, sports nutrition was built around the marathon. A relatively simple effort to understand: high, constant intensity, on stable terrain, for two to four hours. In this context, the recommendations are solid, validated, and almost standardized. The body works like a carbohydrate-burning machine, and the entire strategy is about avoiding running out of fuel.

In trail running and ultrarunning, this logic falls apart.

The intensity is lower, certainly, but it fluctuates constantly. The duration stretches out, sometimes over an entire day or even longer. The terrain becomes unstable, technical, and unpredictable. On top of that, there is cold, heat, altitude, muscle fatigue… and often complex logistics. In other words, this is no longer a race.

It is a physiological expedition.

What your body really experiences in the mountains

Running uphill is nothing like running on flat ground. As the gradient increases, your body consumes more oxygen, breathes harder, and your heart rate rises. Energy expenditure increases in an almost linear fashion. At the same pace, you expend more energy.

Conversely, descents may seem “easy” from a cardiovascular standpoint… but they generate significant muscle fatigue, which eventually affects your ability to maintain your effort, as well as your ability to fuel properly.

And between the two, there is the terrain. Uneven, unstable, and sometimes technical. This factor alone is enough to significantly increase overall energy demands, even without changing pace.

The result: in trail running, your body expends more energy, for longer, and in a much more

chaotic way.

During an ultramarathon, it is not uncommon to exceed 10,000 kcal expended in a single day. An immense energy deficit… that you will never be able to fully make up during the race.

Carbohydrates: essential, but not in the same way

In road running, the reasoning is clear: the longer the effort lasts, the more you need to increase your carbohydrate intake. Recommendations generally range from 30 to 90 g/h, with high intakes strongly correlated with marathon performance.

In trail running, the reality is more nuanced.

Yes, carbohydrates remain essential. They fuel high-intensity phases, climbs, and surges. But very high intakes, around 90 g/h, are rarely achieved in practice. Not because they would be useless, but because they are often difficult to tolerate.

Digestive issues are common. Jostling, duration, heat, the concentration of drinks, and the foods offered at aid stations can disrupt a digestive system already under considerable strain. That is why, in practice, many trail runners consume around 30 g/h, sometimes a little more. Current recommendations also often point toward a range of 30 to 50 g/h, with the option to increase this further if and only if it has been practiced and well tolerated. Because in trail running, one truth quickly becomes clear: what you cannot digest is of no use to you.

The decisive factor: your digestive system

This is probably the most underestimated aspect. In marathons, nutrition is mainly a matter of dosage and timing. In trail running, it becomes a matter of tolerance. Your gut is subjected to constant stress: reduced blood flow, vibrations, and overall fatigue. Add concentrated gels, rich foods, or hydration mistakes, and problems quickly arise.

That is why scientists now emphasize a key concept: “ gut training ”, or digestive system training. Like your legs or your heart, your gut can be trained. It learns to absorb more carbohydrates, better tolerate certain foods, and function under stress. This takes time, trial and error, and adjustments... but it is often what makes it possible to reach the next level in ultrarunning.

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Eating on the trail is also a matter of variety

As the duration increases, another reality emerges: it becomes difficult to rely solely on sugary products.

Palate fatigue sets in. The body craves something else. And that is where trail running once again differs from the marathon.

Over long distances, it is relevant to include:

Salty foods
A little fat
Sometimes protein, in small quantities

Not to replace carbohydrates, but to maintain the desire to eat, provide variety, and better manage satiety. This dietary flexibility is essential, especially in the mountains, where aid stations, what you carry, and the conditions directly influence what you can consume.

Hydration: finding balance

Hydration follows the same logic of adaptation.

On the road, strategies are relatively precise, with a clear objective: to limit

dehydration without going too far. On the trail, needs vary enormously depending on temperature, altitude, intensity, and duration. Intake is generally around 450 to 750 mL per hour, with particular attention to sodium, especially in hot conditions or during prolonged exertion. Once again, the aim is not to apply a strict rule, but to build a strategy that is consistent with how your body works

IN CONCLUSION

What all this changes, concretely

Ultimately, the difference between road and trail isn't only about the numbers. It's about philosophy. On the road: you optimize; on the trail: you adapt.

The goal is no longer simply to maximize carbohydrate intake or follow a precise plan. It's about managing enormous energy expenditure in an unstable environment, while preserving your ability to keep eating. It's a subtle balance between performance, digestive tolerance, logistics, and how you feel.

Science gives us valuable guidelines, but it acknowledges this itself: in trail and ultrarunning, strategies must remain flexible and individualized.

Because the mountains don't follow a plan.

Because your body doesn't either.

And because, ultimately, the person who goes the farthest isn't necessarily the one who consumes the most carbohydrates, but the one who finds the strategy they can sustain, hour after hour, all the way to the finish line.

SOURCES

- Burke, L., Jeukendrup, A., Jones, A., & Mooses, M. (2019). Contemporary Nutrition Strategies to Optimize Performance in Distance Runners and Race Walkers. International journal of sport nutrition and exercise metabolism, 29 2, 117-129 . https://doi.org/10.1123/ijsnem.2019-0004.

- Jeukendrup, A. (2011). Nutrition for endurance sports: marathon, triathlon and road cycling. Journal of Sports Sciences, 29 , S91 - S99. https://doi.org/10.1080/02640414.2011.610348

- Nikolaidis, P., Veniamakis, E., Rosemann, T., & Knechtle, B. (2018). Nutrition in ultra-endurance: state of the art. Nutrients, 10 . https://doi.org/10.3390/nu10121995

- Jiménez-Alfageme, R., Garrone, F., Rodriguez-Sanchez, N., Romero-García, D., Sospedra, I., Giménez-Monzó, D., Ayala-Guzmán, C. et Martínez-Sanz, J. (2025). Nutritional intake and timing of marathon runners: influence of athlete characteristics and fueling practices on finishing time. Sports Medicine - Alberta, 11. https://doi.org/10.1186/s40798-024-00801-w .

- Tiller, N., Tiller, N., Roberts, J., Beasley, L., Chapman, S., Pinto, J., Smith, L., Wiffin, M., Russell, M., Sparks, S., Duckworth, L., O'Hara, J., Sutton, L., Antonio, J., Willoughby, D., Tarpey, M., Smith‐Ryan, A., Ormsbee, M., Ormsbee, M., Astorino, T., Kreider, R., McGinnis, G., Stout, J., Smith, J., Arent, S., Campbell, B. et Bannock, L. (2019). International Society of Sports Nutrition position stand: nutritional considerations for single-stage ultra-marathon training and competition. Journal of the International Society of Sports Nutrition, 16 . https://doi.org/10.1186/s12970-019-0312-9

- Aktitiz, S., Kuru, D., Ergün, Z. et Turnagöl, H. (2024). Nutritional strategies for single- or multi-stage ultra-marathon training and competition: from theory to practice. Turkish Journal of Sports Medicine. https://doi.org/10.47447/tjsm.0807